It depends on calling ranges.
If they are only calling with 55+ AT+ then 86 is better. If calling range includes lots of K-high and Q-high hands, than A5 is probably slightly better.

Although I looked at some charts, there are NOT many ranges where 86 is better. AA.
I think if you throw in pairs <AA as a large part of calling range, A5 is better.

This seems to be true with A5o vs 86s as well.

That's assuming you see all 5 cards. Post flop, I guess 86 is much easier to play.